Your DS is in a difficult position. It's really frustrating to watch such apathy and inaction, but it's part of the illness, unfortunately.
It generally isn't possible to do retakes of third year, as it's the final year.Most universities measure 'exit velocity' in some way, recognising that students are likely to be better in third year than second year, and so on.
But my sense is that trying to cobble something togeher now is pretty pointless. His health needs to be his first priority. People still seem to havethe idea that university is "easy" -- an extended adolescent time at school. It's not. It's tough, you need to be tough, and that's entirely as it should be. University is training the next generation of professionals, thinkers, leaders. Students need to be healthy & resilient. His current illness attacks both those aspects of his character (a sort of anemia, I always think).
Knowledge is power in these situations. He needs to know what his options are. Not for now, because he sounds like he needs to ficus on becoming well again, and - if his illness is chronic - how to cope with it, in terms of triggers, lifestyle etc, as well as medication & therapy.
- He should enquire about how long the credit points from his two years of study (1st & 2nd year) will remain 'live' so that when he's well enough, he can resume studies, either at his current university or another one.
He should enquire about back-dating a leave of absence/intercalation/interruption of studies (universities call this differnt things) so that he could return to his current university when he's coping better with hs health. And redo* the entire 3rd year. Frankly, from what you say, there's not much to rescue from his work this year.
He'll need to act quickly the month of Exam Boards is upon us. He'll need to be absolutely frank about his struggles with his illness. THis is difficult, particularly with a mental, rather than physical illness. He'll need to be frank about why he didn't seek help or mitigation before. Why students don't do this is incredibly frustrating from a tutor's pov, but understandable. However, we are bound by regulations, which exist so that all students are treated fairly. I once worked at a place that required evidence of a family death if this was being claimed as a mitigating factor there'd been too many "dead grandmothers." It seems inhuman, but it keeps everyone safe.
But he needs to be frank and open. His personal tutor first, or head of year, or Exams Officer. THe Departmental secretary/administrator will know. THey are generally the most knwledgeable person in any Department! (mine tell me what to do, thank goodness).